A Fiftieth Year Retrospective on the 1976 Mw 7.5 Motagua Earthquake in Guatemala

ABSTRACT On 4 February 1976, an Mw7.5 earthquake ruptured ∼240 km of the Motagua fault in Guatemala, causing ∼23,000 fatalities. This event provided evidence for the fault’s role as a major transform boundary between the North American and Caribbean plates. Field observations, seismological analyses, and postseismic studies helped constrain fundamental aspects of the 1976 earthquake mechanics and the spatial complexity of the rupture. This event opened a window for studies documenting past deformation along this plate boundary across multiple spatial and temporal scales. Five decades of research have established this earthquake as an important event for understanding strike-slip ruptures along major plate boundaries. This review integrates legacy field observations, subsequent analyses, and recent investigations along the North American and Caribbean plate boundary in Guatemala. Our goal is not only to synthesize the details and highlight the importance of the event but also to preserve essential datasets that continue to inform our understanding of plate boundary mechanics, seismic hazard, and the long-term behavior of this major transform fault system.